High-density recording on multiple tracks of a magnetic tape is known. In certain arrangements, parallel tracks extend along the longitudinal length of the magnetic tape. Magnetic tape is moved transversely across a read/write head so that a read and/or write element of the read/write head is moved in proximity to the desired track. During recording or playback, the read/write elements of the read/write head should be aligned with the desired track as the tape moves in a longitudinal direction across the read/write head bump. To increase storage capacities, track density, which is the number of tracks per distance (e.g., inches), has gradually increased. As this track density increases, the track pitch and width decrease. For proper read/write operation, the read/write element of the read/write head should stay at, or very near, the center line of the track. Due to this reduced track pitch, improvements to the head positioner are needed to minimize the offset between the read/write elements of the read/write head and the center line of the track. To that end, servo-based tracking systems employed to allow the tape drive to monitor the head-to-track relationship. If the drive determines that the head and track are offset, then the head positioner corrects the relative position to maintain the relationship between the read/write head and the center line of the track.
Closed loop positioners are often used in tape systems having higher track densities. In high-density tape systems, the tape may wander in the lateral direction as it moves in the longitudinal direction, which results in an offset between the read/write head and the track center line. To avoid these types of problems, tape cartridges for high-density tape drives are preformatted with information often called servo information, which is used to maintain the correct lateral position of the tape with respect to the read/write head. Servo information provides the system with feedback to determine the continuous position of the tape relative to the read/write head. Analysis of the servo signals allows for a determination of an offset and the distance of the offset between the expected track location and the actual read/write head position. Based on the information, the read/write head is moved by a positioner to the center line of the track so that write/read operations can occur properly. Closed loop positioners generally use fine positioners to move the read/write head during a write/read operation. These fine positioners are used to maintain the position of the read/write head at the center line of the track under a closed loop servo control using the preformatted servo information on the tape.
The tracking servo system employed by linear tape drives, such as the Linear Tape Open (“LTO”) family, is an example of a servo-based, closed loop control mechanism that allows for increased track density. Track density is one of the parameters, besides bit density, that allows storage capacity to increase. The tracking servo system requires feedback to indicate the relative position of the tape and the recording head elements. One of the methods employed in linear tape drives using such feedback signals is to pre-record a series of magnetic stripes that contain position feedback information, which is a timing-based signal. When the stripes are recorded with predetermined azimuth angles, the signals from the read/write head can be processed to decode the lateral position information regarding the relative position of the read/write head and the tape.
The increasing track density typically requires improvements in tape drive manufacture specifications. Two of these specifications include zenith (x-axis) and azimuth (y-axis tilt) of the read/write head. If the zenith and/or the azimuth is not properly calibrated, accuracy of transducing data on a tape decreases.
One prior art approach for calibrating the zenith and azimuth is an optical alignment system that utilizes a camera to digitize points of the read/write head in order to determine the zenith and azimuth. Once those values are known, the optical alignment system further manipulates screws, if necessary, to calibrate the zenith and azimuth. However, optical alignment systems are typically very expensive. Additionally, they are typically not robust enough to accurately calibrate read/write heads of next-generation technologies.